ATLANTA – Combination therapy with ibrutinib and venetoclax is well tolerated and shows promise for the treatment of relapsed/refractory chronic lymphocytic leukemia (CLL), according to initial results from the CLARITY feasibility trial.
Of 38 patients who received at least 6 months of treatment with combination ibrutinib (Imbruvica)/venetoclax (Venclexta) and reached month 8 – and therefore had computed tomography, clinical data, and peripheral blood and marrow assessments available – 15 (37%) achieved peripheral blood minimal residual disease (MRD) negativity, and 12 (32%) achieved bone marrow MRD negativity, , reported during a press briefing at the annual meeting of the American Society of Hematology.
The rates of MRD negativity in the blood and marrow, and of normal trephine biopsy, were similar in subsets of patients who relapsed within 36 months of prior treatment with fludarabine/cyclophosphamide/rituximab (FCR) or bendamustine/rituximab (BR), and with prior idelalisib exposure, he noted.
“In terms of [International Workshop on Chronic Lymphocytic Leukemia] response criteria, which is a secondary endpoint, 47% of patients achieved a [complete remission or complete remission with incomplete hematologic recovery] and every patient has had an overall response, which for this group of patients is impressive,” he said.
Again, the findings were similar in those who were refractory to prior FCR/BR or to previous idelalisib, he noted.
Both ibrutinib and venetoclax are approved as single agents for the treatment of CLL. Ibrutinib is a Bruton’s tyrosine kinase inhibitor that has had a major effect on patient outcomes, showing overall survival advantages in numerous trials, Dr. Hillmen said.
“However, ibrutinib does not eradicate disease, and patients remain on treatment indefinitely or until progression,” he said.
Venetoclax is a highly selective B cell lymphoma–2 inhibitor approved for refractory CLL in patients with 17p deletion. It has a rapid effect, which can lead to tumor lysis syndrome, but also leads to eradication of MRD in some patients, which can lead to prolonged survival, he said.
Thewas designed to investigate the safety and efficacy of the two in combination in relapsed/refractory CLL patients.
The primary endpoint of the study is MRD eradication in the marrow after 12 months of treatment. The current analysis looks at a key secondary endpoint of the study – MRD eradication in the marrow after 6 months of treatment.
The study enrolled 54 patients, including 37 men and 17 women with a median age of 64 years; 20% have 17p deletion, and the population was heavily pretreated, with 81% having prior FCR or BR (44% with relapse within 3 years of treatment), and 20% with previous idelalisib exposure. Patients were excluded if they had prior exposure to ibrutinib or venetoclax.
Treatment involves ibrutinib monotherapy at a dose of 420 mg/day for 2 months to debulk the disease, after which venetoclax is added at a dose escalating from 20 mg to 400 mg/day over 2 months to reduce the risk of tumor lysis syndrome.
Bone marrow biopsies are performed at 6, 12, and 24 months. Treatment is discontinued at 12 months in those who achieve MRD negativity at 6 months, and is discontinued at 24 months in those who achieve MRD negativity at 12 months.
The combination treatment was well tolerated in the first 38 patients. Bruising (mainly grade 1) occurred in 33 patients, and neutropenia (including 16 grade 3 cases and 6 grade 4 cases) occurred in 25, and some GI toxicity occurred, but was largely grade 1 or 2, Dr. Hillmen said.
“There really was otherwise very acceptable toxicity,” he added, noting that a single case of tumor lysis syndrome occurred, but was managed successfully by delaying venetoclax.
“That patient re-escalated back onto treatment and is doing well,” he said.
No patients stopped treatment, and only seven had treatment interruption, and then only for a few days, he noted.
The findings are encouraging, and suggest a potent synergy between ibrutinib and venetoclax, said Dr. Hillmen.
“We’re seeing, even at this very early stage, over 30% of patients achieving MRD negative remission, which was our target at the 12-month bone marrow stage with this combination,” he said.
In light of these results, the ongoing phase 3, which is actively recruiting, has been modified to include combination ibrutinib and venetoclax in front-line CLL, he said.
Dr. Hillmen reported financial relationships with AbbVie and several other pharmaceutical companies. The CLARITY trial is supported by AbbVie, Bloodwise, Experimental Cancer Medicine Centre, Janssen-Cilag, the National Institute for Health Research Clinical Research Network: Cancer, and the University of Birmingham (England).
SOURCE: Hillmen P et al., ASH .